Quantum Criticality: Topology, Order, and Metallicity

量子临界性：拓扑、有序和金属性

• 批准号: RGPIN-2019-04502
• 负责人: Aronson, Meigan
• 金额: $ 3.64万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737667
• 关键词: Quantum; Criticality; Topology; Order; Metallicity

Metals are familiar to us in daily life, where the motion of electrons serves to conduct heat and electricity, in applications as diverse as cookware, microelectronics, and power distribution. Insulators are the opposite, where the absence of mobile electrons prohibits heat and electric currents. Recently, a new hybrid class of materials has been discovered where the interior of the material is insulating, while its surface readily conducts electricity and heat, but in ways that are distinct from normal metallic conduction. These materials are called topological insulators, and the separation of the surface and bulk conduction results from the topology of the electron states, where the bulk and surface states are as different as a sphere and a torus. The insulating interior restricts the mobile electrons to the surface, where their motion either covers the surface or must follow looplike orbits. These constraints make it nearly impossible for the electrons to change their energies, and so they conduct heat and electricity with significantly less dissipation than the three-dimensional electron motion found in normal metals. Interest in topological materials stems from their potential to reduce the power consumption of electronic devices, and to enable novel energy conversion devices. If the surface states are superconducting, they may form long-lived quantum states which could be the fundamental units of quantum information technologies. Before these technologies and others can be realized, there is a pressing need to understand how these topological constraints work and can be controlled. Our research seeks new materials where the topological character can be continuously modified by pressure or composition, and indeed entirely suppressed at a topological phase transition that separates conventional insulators without conduction from topological insulators with robust surface conduction. How does conduction emerge as the surface state is established, and the electrons transform from being spatially localized to completely mobile? Where is the conduction the largest and most sensitive to external forces? What are the thermodynamics that stabilize topological phases, and how do quantum fluctuations oppose them? Can we combine topological phases with more familiar sorts of order such as magnetism or superconductivity? We will use a variety of different electrical transport measurements backed by our arsenal of magnetic, thermal, and neutron scattering capabilities to address these questions in this research project. We will use the latest advances in crystal design to discover and modify new materials where we can explore these novel properties of topological insulators.

金属在日常生活中是我们所熟悉的，其中电子的运动用于导热和导电，在炊具，微电子和配电等各种应用中。绝缘体则相反，由于没有移动的电子，热量和电流都无法通过。最近，发现了一种新的混合材料，其中材料的内部是绝缘的，而其表面容易导电和导热，但与正常的金属传导方式不同。这些材料被称为拓扑绝缘体，并且表面和体传导的分离是由电子状态的拓扑结构引起的，其中体和表面状态就像球体和环面一样不同。绝缘的内部将移动的电子限制在表面，在那里它们的运动要么覆盖表面，要么必须遵循环状轨道。这些限制使得电子几乎不可能改变它们的能量，因此它们传导热和电的耗散比正常金属中的三维电子运动要少得多。 对拓扑材料的兴趣源于它们降低电子器件功耗和实现新型能量转换器件的潜力。如果表面态是超导的，它们可能形成长寿命的量子态，这可能是量子信息技术的基本单元。 在实现这些技术和其他技术之前，迫切需要了解这些拓扑约束是如何工作和控制的。我们的研究寻求新材料，其中拓扑特征可以通过压力或成分不断修改，并且确实在拓扑相变中完全抑制，该拓扑相变将没有传导的常规绝缘体与具有强大表面传导的拓扑绝缘体分开。当表面状态建立，电子从空间局域化转变为完全移动的时，导电是如何出现的？哪里的传导最大，对外力最敏感？什么是稳定拓扑相的热力学，量子涨落如何对抗它们？我们能否将联合收割机拓扑相与我们更熟悉的有序性（如磁性或超导性）结合起来？我们将使用各种不同的电输运测量支持我们的武库的磁，热和中子散射能力，以解决这些问题，在这个研究项目。我们将利用晶体设计的最新进展来发现和修改新材料，在那里我们可以探索拓扑绝缘体的这些新特性。